core

## Checking and Fixing Point Nominal Deviation

Point Nominal Deviation dialog box

The Edit | Graphic Display Window | Point Nominal Deviation menu option displays the Point Nominal Deviation dialog box. Use this re-sizable dialog box to compare certain point measurements against a CAD model to check for changes or updates made to the CAD model. Essentially, you define a tolerance value, and PC-DMIS looks at the nominals for any point features in your measurement routine and compare them against the CAD model.

PC-DMIS lists all of the points. It lists any points that deviate beyond the defined tolerance value in a red/orange color; you can then adjust them as needed.

The Point Nominal Deviation dialog box contains the following options:

Deviation cutoff - This box filters the point features that display. The distance between a point feature's theoretical position and the CAD model nominal position is its deviation. Only points whose deviation is greater than or equal to the deviation cutoff are listed.

Angle deviation cutoff - This box controls the nominal CAD position. The CAD surface normal and the point vector must be within this angle. The range for this angle is 0–90 degrees.

Find nominals tolerance - This box defines the tolerance value that are allowed for each point feature. Points with a deviation that exceeds this tolerance value turn red.

Search priority surfaces - This check box specifies whether or not PC-DMIS only uses priority surfaces when searching for a solution. You can define priority surfaces using the Set as priority check box in the Edit CAD Elements dialog box. See the "Editing CAD" topic for more information on how to do this. If you clear this check box, and PC-DMIS cannot find an acceptable value within the defined priority surfaces, it checks all of the other surfaces on the CAD model.

Update - This button lists all of the points on the CAD model.

Move Checked Features - This button updates the XYZ and IJK values of those point features whose check boxes you have selected to match the CAD model's XYZ and IJK values.

Copy Checked to Clipboard - This button copies the information about all of the selected points to the Clipboard. For an example, see "Clipboard Example".

Override - Sometimes the best point that the algorithm finds is incorrect. When you select a single feature, the Override button becomes available. Click this button to display the Override dialog box, which you can use to override the found point with a different point. For more information, see "Using the Override Dialog Box".

Feature - This column displays the name of the ID of the feature. The column's header contains a check box. Selecting or clearing this check box selects or clears the check boxes for all point features in the list.

Current XYZ - This column displays the feature's current theoretical position.

Current IJK - This column displays the feature's current theoretical vectors.

CAD XYZ - This column displays the feature's nominal position if it were moved onto the CAD.

CAD IJK - This column displays the feature's nominal vector if it were moved onto the CAD.

Deviation - This column displays the distance between the feature's current theoretical position and its corresponding nominal CAD position.

Angle Dev - This column displays the angle deviation between the feature's current theoretical vector and its corresponding nominal CAD vector.

Clipboard Example

Feature Current XYZ Current IJK CAD XYZ CAD IJK Deviation Angle Dev
PNT1 (3.8,3.902,0) (0,0,1) (3.8,3.902,0) (0,0,1) 0 0
PNT2 (4,0.23,0) (0,0,1) (4,0.23,0) (0,0,1) 0 0
PNT3 (8.3,1.91,0) (0,0,1) (8.3,1.91,0) (0,0,1) 0 0
PNT4 (2,0,-0.67) (0,-1,0) (2,0,-0.67) (0,-1,0) 0 0
PNT5 (6.36,0,-0.45) (0,-1,0) (6.36,0,-0.45) (0,-1,0) 0 0
PNT6 (3.33,0.978,1.5784) (-0.6591,0.4865,0.5735) (6.665,3.3021,-0.497) (-0.7205,0.2411,0.6502) 4.5641 15.1919
PNT7 (0.2056,1.75,0.555) (0.2579,-0.1052,0.9604) (0.2058,1.7499,0.5558) (0.2622,-0.1008,0.9597) 0.0009 0.3552
PNT8 (9.2,1.9685,-0.5027) (0,-1,0) (9.2,1.9685,-0.5027) (0,-1,0) 0 0
PNT9 (9.4094,1.28,-1.234) (1,0,0) (9.4094,1.28,-1.234) (1,0,0) 0 0

Example of points copied to Clipboard (Best viewed full screen)

Using the Override Dialog Box

Override dialog box

The Override dialog box appears when you select the Override button in the Point Nominal Deviation dialog box. It shows a list of all of the CAD nominal points that correspond to the selected feature from all surfaces within the Find Nominals Tolerance search zone. PC-DMIS initially sorts these points from the smallest to the largest deviation. Usually, the first point that is listed is the point used in the Point Nominal Deviation dialog box. Each point is graphically represented with a cross-hair in the Graphic Display window.

Selecting a point in the list highlights that point as well as any curve or surface on which the point lies in the Graphic Display window. Once you find the desired point, click the Override button. The Override dialog box closes and the Point Nominal Deviation dialog box reappears, showing the updated point value.

Use previous surface - You should use this check box when you override several points. For example, if you know that points for several features should all lie on the same surface but the algorithm incorrectly put the points on different surfaces, you would override the first feature as usual. Then on the second and subsequent overrides, you could select the Use previous surface check box. This would cause PC-DMIS to only show the points found on the surface of the previous override.

Find nominals tolerance - This box functions the same as the box with the same name in the Point Nominal Deviation dialog box, but with different results. PC-DMIS searches the CAD for nominal points that correspond to the selected feature. It searches in a spherical zone around the current theoretical position of the selected feature. This box defines the size of that spherical search zone. The value regulates the amount of CAD that PC-DMIS evaluates while generating this point override list.

The Search priority surfaces only check box is discussed in the table above.